Note: Descriptions are shown in the official language in which they were submitted.
~ 6 T-7249
Background of the Invention
The present invention relates to the art of induction
heating and, more particularly, a method and apparatus for
hardening axially spaced cams on a camshaft of the type used
in internal combustion engines.
The invention is particularly applicable for inductively
heating the axially spaced cams on an automobile engine cam-
shaft formed from forged steel and it will be described with
particular reference thereto; however, the invention has much
broader applications and may be used for inductively heating
the axially spaced cams on a variety of camshafts formed from
various types of ferrous material.
Within the last few years, there has been a substantial
demand for highly efficient, high performance internal
combustion engines to be used in vehicles wherein the engine
must have a reduced, combined rotational friction and be
capable of operating at relatively high rotational velocities.
Further, these engines must be reduced in weight and relatively
simplified to thereby decrease the overall weight-to-horsepower
ratio of the engine, so that fuel economy can be optimized.
All of these commercial factors, together with foreign
competitive situations, has resulted in a substantial amount
of effort devoted to designing and manufacturing each component
in the engine. One of the more critical components in an
internal combustion engine is the rotating camshaft, which
shaft has a plurality of axially spaced cams, each with a lobe
that actuates a valve during operation of the engine. To
decrease friction and increase rotational speed, it has been
decided by many engine manufacturers to employ a roller
follower adapted to contact the outer eliptical or eccentric
surface of each cam to transmit the cam action to the valve
itself. These roller followers exert a substantial force
against the cam surface as the camshaft is rotated. In
addition, due to the speed of operation, the cam surfaces
1~ 01 ~6 ``
must be very accurately controlled in dimensional character-
istics to provide the efficient operation of the valve during
engine operation. To accommodate the wear and provide
dimensional accuracy, it has, in the past, been somewhat
common practice to manufacture the camshaft from cast iron.
The cams of the cast iron camshaft were then machined and
hardened by first inductively heating the cam surface by
surrounding inductor and then quench hardening the heated
surface. To increase production, which is always an essential
element of this type of equipment, devices such as those shown in
the U.S. Patent to sober 3,944,446 and Laughlin et al
3,784,780, were developed by assignee of this application.
Also, carbonized hardening processes were employed.
Further, induction heating of all cams at the same time with
plunge quenching was used for the purpose of heating the
various camshafts. In these instances, the camshaft was
rotated to provide uniformity. In addition,
relatively low power densities were employed, below about
10 KW/in , so that the hardened depth of the various cams
was somewhat deep. All these processes required subsequent
grinding and stoning for the purposes of generating the final
cam surfaces, which must be done accurately. In other words,
the hardened surfaces had to have a sufficient depth to
facilitate actual generation of the cam surfaces subsequently
by grinding and/or stoning. These post hardening processes
necessitated relatively deep hardness and resulted in tools
which needed dressing or changing after short periods of
operation. All of these problems drastically increase the
cost of the camshaft and often resulted in a cast iron
hardened surface which was not sufficiently rigid to support
high speed roller operations. This general situation required
a re-thinking of camshaft technology for internal combustion
engines of the type used in modern motor vehicles.
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1~8~176 T-7249
One of the solutions to the problems was eo produce a
forged steel camshaft blank which could be machined, inductively
heated on the bearing surfaces of the cams, and then quench
hardened, following by at least a stoning operation. The
theory was, among other things, that the steel camshaft would
have sufficient surface stability after hardening to operate
in modern day motor vehicles. In addition, the steel camshafts
could apparently be somewhat reduced in weight. All of these
attributes contributed to the selection of this type of cam-
shaft for use in the more recently manufactured engines for
motor vehicles, at least for the United States market. Many
people used the prior induction heating devices for the purpose
of hardening the cams and also the fuel pump gear on the cam-
shafts. Generally, the bearing surfaces concentric with the
rotational axis of the camshaft could be left fairly soft
since they presented a substantial area for support by axially
spaced bearing blocks. Assignee of applicants, through
applicants, embarked upon a revolutionary new approach for
the purposes of hardening the surface of cams axially spaced
along the camshaft, which process would overcome all of the
disadvantages resulting from the mere attempt to use prior
induction heating technology for these revolutionary new
and technically complicated hardening problems. Applications
of known technology did not produce camshafts at a production
rate- or quality meeting the present day demand. The present
invention utilizes an approach described generally in the
SAE technical paper series, No. 860231, entitled "Post Grind
Hardening, an Alternative Method of Manufacturing a Steel
Roller Camshaft".
The Invention
The present invention relates to a mac~ ne culminating in
the development of a process and apparatus for using induction
heating to produce camshafts which have the cams individually
induction heated and then quench hardened in a manner producing
dimensional stability, substantially uniform hardening and at
a rapid rate concomitant with production requirements by the
automobile industry.
~ 176 T-7~4g
The primary ob~ect of the present invention is the
provision of a method and apparatus for hardening the
suriEaces of axially spaced cams on a camshsft, which method
and apparatus produce uniformly hardened, dimensionally
stable surfaces at a high production rapid rate and with a
low amount of scrap.
Another object of the present invention is the provision
of a method and apparatus, as defined above, which method and
apparatus utilizes a single induction heating coil having its
own power supply for energizing the coil as the coil surrounds
the cam surface.
Yet another ob~ect of the present invention is the
provision of a method and apparatus, as defined above, which
method and apparatus inductively heats a single cam surface
at a rate of between 0.3 to 3.0 seconds and, preferably,
in the neighborhood of about 1.0 second without diminution of
uniformity and without sacrificing quality around the total
surface of the cam.
Another object of the present invention is the provision
of a method and apparatus, as defined above, which method and
apparatus results in cam surfaces which require no post grinding
for generating the axial cam surface and diminishes the amount
of post stoning needed for finishing the surface of the various
cams.
Yet a further object of the present invention is the
provision of a method and apparatus, as defined above, which
method and apparatus inductively heats each cam surface while
it is held in an indexed position by an induction heating coil,
which coil has its heating characteristics modified or controlled
by flux concentrations so that the indexed position of the cam
surface is a fixed position commensurate with the necessary
heating pattern and hardness pattern associated with the
particular heating coil. In accordance with the preferred
embodiment, the nose, tip or lobe of the cam is pointed toward
the fishtail or insulation gap in the induction heating coil.
i~Oi7 6 T-7249
In accordance with this aspect of the invention, on
high power, exceeding ~5 KW/in2 for a short time, in
the neighborhood of 1~0 second, can inductively heat
the total surface of the cam for immediate quench hardening
by low volume polymer quench fluid directed at the heated
cam surface through the inductor or heating coil.
Still a further object of the present invention is the
provision of a method and apparatus, as defined above, which
method and apparatus includes an arrangement for scanning
each of the cam surfaces of the camshaft by an eddy current
coil and detecting the electrical characteristics of the coil
eo determine whether or not the various cam surfaces have a
hardness characteristic coming within a preselected acceptable
range of responses at each of the various cams. In accordance
with this ob;ect, the eddy current testing of the various cams
can occur subsequent to sequential hardening of the various
cams and as the cams pass through the eddy current coil.
This non-destructive non-touching arrangement for determining
hardness on-the-fly, when incorporated with the sequential
hardening of the cam surfaces, produces a uniform hardening
process, as described in U.S. Patent 4,618,125.
Another ob;ect of the present invention i8 the provision
of a method and apparatus, as defined above, which method and
apparatus employs a unique combination of coil, cooling assembly
and operable splash plates forming a lower wall below the cam
surface being heated.
Still a further object of the present invention is the
provision of the structure, as defined in the appended claims~
In acc~rdance with the present invention, to satisfy the
above objects, there is provided a method and apparatus for
inductively heating, and then quench hardening, the surfaces of
axially spaced cams on a steel camshaft having a longitudinally
extending rotational axis concentric with a plurality of
axially spaced bearings, each having surfaces concentric to the
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~1~
1;~80176
T-7249
rotational ~is. The cams have lobes with differing cir-
cumferential locations. The invention employs means for
rotatably mounting the camshaft to rotate about a worked
axis coinciding with the rotational axis of the workpiece,
an induction heating coil having an inner surface surrounding
the work axis with an insulating gap and integral quenching
openings for directing, at low volume rate, a liquid inwardly
from the heating coil toward the work axis of the workpiece,
a high frequency (10 KHz - 25KHz) power supply for inductively
energizing the heating coil with a power density within the
heating coil of over about 20 KW/in , an auxiliary cooling
assembly fixed with respect to the heating coil at an axially
spaced position near the heating coil and including means for
spraying a cooling liquid toward the work axis, first drive
means for causing relative axial movement of the camshaft and
the heating coil to position a cam in the heating coil during
a hardening cycle, including an induction heating portion and
a quench hardening portion, second drive means for rotating
the camshaft about the work axis, means for controlling the
second drive means for selectively rotating the camshaft to
an indexed position with the cam in the coil having a pre-
selected fixed circumferential orientation during at least the
heating portion of the heating cycle, which orientation is
preferably with the lobe facing the insulating gap of coil,
means for selectively operating the power supply means during
the heating portion of the cam hardening cycle, means for
selectively operating the cooling assembly during at least
the heating portion of the hardening cycle far a cam in tha
heating coil, control means for repeatedly operating the
first drive means, the second drive means, the power supply
operating means, the cooling assembly and operating means for
axially indexing a further cam into the fix orientation within
the heating coil for hardening during a hardening cycle while
a previously, axially adjacent, cam is cooled in the cooling
assembly. Means are provided for preventing splashing of
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~8Q1~6 T-7~49
the coolin~ liquid into the cam in the heatin~ coil during
the heating portion of the heating cycle.
By processing the cam surfaces individually with high
` power density and a low time, in the range of 0.3 to 3.0
seconds and preferably 1.0 second, the surface is heated
rapidly and immediately quench hardened by an integral
quenching arrangement. There is little time for growth to
distort the surfaces. The high frequency keeps the heating
depth quite shallow and near the surface so that any grain
growth will be minimized by this shallow depth and the rapid
temperature increase and decrease. This processing concept
gives the cam surface little time to grow and has little
heated mass in which to effect growing. Dimensional stability
is maintained so that post grinding is not required. This
stability feature is accomplished by using relatively high
frequency, about 10 KHz, high power factor and short heating
time followed by an immediate liquid quench. This process
is done by a single inductor heating a single surface preparatory
to quench hardening. The quench hardening cycle requires a
volume of liquid, but a very short time; however, high velocity
inpingement is avoided by using larger quenching holes so
there is no abrupt spot quenching caused by high velocity
liquid jets. Heat is to be extracted by the quenching fluid
over the total surface, instead of by mass quenching by core
material behind the heated surface. Each coil has its own
power supply to obtain the high power density. In accordance
with the preferred embodiment of the present invention, two
separate heating and quench hardening assemblies are provided
on parallel axes, each triven by its separate high frequency
power supply. In this manner, production rates can be doubled
by processing two camshafts simultaneously.
A method and apparatus, as defined above, satisfies the
previously mentioned objects and advantages. Other objects
and advantages will become apparent from the following
description used to illustrate the preferred embodiment of
the invention, as read in conjunction with accompanying drawings:
1~8~1~6 T-7249
Brief Description of the Drawings
FIGURE 1 is a front elevational view showing, somewhat
schematically, the preferred embodiment of the present
invention for processing two camshafts C, C' in parallel,
vertical disposition;
FIGURE 2 is a schematic partial view illustrating the
initial shaft locator mechanism and final stamp for an approved
accepted camsha$t;
FIGURE 3 is a graph illustrating, somewhat schematically,
the output of a proximity switch on the locator, as illustrated
in Figure 2;
FIGURE 4 ~s an enlarged, cross-sectional view ta~en
diametrically through a portion of the camshaft after hardening
and illustrating the hardness pattern at the heel and lobe of
one cam surface;
- FIGURE S is an enlarged, cross-sectional view showing
the integral quench, cooling assembly and plate concept employed
in the present invention;
FIGURE 6 is a view taken generally along line 6-6 of
Figure 5 with several partial cutaways to illustrate certain
concepts of the assembly shown in Figure 5~
FIGURE 6A is a cross sectional view of the coil and
the ~uench unit of the current preferred embodiment;
FIGURE 6B is a cross sectional view taken generally along
the line 68-6B of Figure 6A;
FIGURE 6C is a flux childlng element used in the structure
of Figures 6A and 6B;
FIGURE 7A - 7H are views showlng various steps through
which the mechanism and method process for the purposes of
processing camshafts in accordance with the invention;
FIGURE 8 is a top view illustrating the induction heating
coil as used to heat a rotating workpiece, such as the fuel
pump gear of camshafts;
: FIGURE 9 is a block diagram illustrating the general
micro-processor controlled concept employed in the present
invention;
FIGURE 10 is an enlarged detailed partial view showing
the lower head of the camshaft mounting mechanism;
_g_
T-7249
FIGURE 11 is a block diagram showing the proce~sing
steps employed in the present invention;
FIGURE llA is a further block diagram showing the
concept used in testing the previously hardened cam surfaces
on-the-fly by a somewhat standard eddy current detector
arrangement, one of which is illustrated in Patent No.
4,230,987;
FIGURES 12 and 12A are eddy current mapping arrangements
which illustrated the operating characteristics of ehe eddy
current testing device constructed in accordance with the
present invention; and,
FIGURE 13 is a partial plan view showing certain aspects
of the eddy current testing device used in the preferred
embodiment of the present invention.
Preferred Embodiment
Referring to the drawings where the showings are for
the purpose of illustrating the preferred embodiment of
the invention only, and not for the purpose of limiting same,
device D shown in Figure 1 is employed for hardening the
cam surfaces on a camshaft C. In the preferred embodiment
of the invention, a second camshaft C' i8 processed in
unison with camshaft C by the same arrangement and mechanism;
therefore, only camshaft C will be described in detail and
the same description will apply equally to the parallel
camshaft C'. Camshaft C is formed of forged steel and
includes a longitudinally extending axis x and has axially
: spaced bearing surfaces 10, 12, 14, 16 and 18. Of course,
various types of camshafts, with a variety of cams, can be
processed in accordance with the present invention by device
D and the particular camshaft herein illustrated is for the
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~X801~6 T-7249
purposes of description only and not for any limitation on
the inventive concepts. The camshaft employs cams 20 axially
spaced along axis x with each cam having a heel 24 and a
lobe 26, which lobe extends outwardly in a radial direction
greater than the heel 24. The orientation of lobes 26 of
the various cams 20 is circumferentially different, to
operate cams in accordance with standard technology. These
cams each include outer surfaces 22 which are to be inductively
heated and then quench hardened to provide a hardness pattern P
as shown in Figure 4. This pattern extends axially across
the width A of cam 20 and inwardly a distance B. The short
heating and then immediate quenching causes the depth b to be
nearly the reference depth caused by the power supply frequency.
Low depth and short time results in a short burst of energy.
With the energy affecting the distortion in a direct relation-
ship, processing as employed in the invention minimizes such
distortion. In accordance with the preferred embodiment of
the invention, the depth _ is generally uniform around surface
22. This is accomplished by holding the cam stationary within
the induction heating coil during the induction heating process
and positioning the cam and coil with respect to various flux
concentrating devices to produce a uniform hardness pattern P.
The heating cycle i8 accomplished by a high power density
heating process providing at least 20 KW/in at ~urface 22 and,
preferably, in the neighborhood of 50 KW/in . This high power
density occurs for only a short period of time between 0.3 and
3.0 second~, and preferably 1.0 second. Consequently, depth
b is controlled primarily by the frequency of the power supply
used in the heating operation. In practice, this is between
10 KHz and 25 KHz. The greater the frequency, the smaller
the distance b. Since the heating cycle is high power and low
time and the surface is immediately quenched by high flow
liquid, the thickness of the hardness pattern is basically
determined by the frequency of the heating operation. As the
frequency increases, the thickness decreases; therefore, the
frequency is selected between 10 KHz and 25 KHz for the purposes
-11 -
.
1~80176 T-7~49
of controlling the desired thickness which is immediately
frozen by subsequent liquid quenching. This combines with
the normal mass quenching to preclude growth of the metal
in the hardness pattern.
Camshaft C includes an upper end surface 28 having a
center countersink 30 on axis x and an axially spaced locator
bore 32. A bottom locator surface ~0 includes a coun~ersink
42 on axis x. In accordance with normal practice, the
camshaft also includes a fuel pump gear 44, which is to be
hardened. Bearings 10-18 in this illustrated embodiment
are not hardened.
Referring now to device D, it includes a fixed frame 50
having vertically extending rods or posts 52, 54. A down-
wardly extending screw 60 is rotatably mounted in spaced
journals 62, 64 by motor Ml. This motor can be rotated in
both directions and to any selected angular position, usually
rotation is contracted by counting pulses from an encoder
associated with Motor M. On fixed frame 50 is mounted a
movable frame 70 reciprocally received on rods 52,54 by an
upper plate 72 and a lower plate 74 secured together as a
unit by a vertical standard 76. As so far described, frame 70
reciprocates on rods 52,54 by appropriate journals in plates
72, 74. Plate 72 i9 secured with respect to feed screw 60 by
a nut section or portion 80. Rotation of screw 60 moves frame
70 along rods 52, 54 by the interaction between the nut section
80 and threads on screw 60. As so far described, as motor Ml
is rotated, movable frame 70 is reciprocated with respect to
fixed frame 50. Motor Ml i9 a servo-motor movable in both
directions and accurately positioned at any angular disposition
to determine accurately, in accordance with standard practice,
the vertical position of the movable frame 70 on fixed frame 50.
The mounting arrangement for the camshaft includes an
upper head 100 secured to plate 72 and a lower head 102 secured
to plate 74. These heads are schematically illustrated in
Figure 1 for the purposes of explaining the operation of device
T-7249
D; however, certain details of the lower head are shown in
Figure 10~ Upper head 100 includes a spindle 110 rotated
by drive motor M2 having two modes of operation, one mode
indexes the spindle in a circumferential direction and
the other mode allows continuous rotation of the spindle.
This type of drive motor is a standard servo-motor, which is
used to accurately position elements and which allows
continuous rotation according to the input signal. Details
of motor M2 form no part of the present invention.
Spindle 110 is rotatably mounted in ~ournal post 112
and an actuator 114 moves the spindle upwardly to allow
loading of the camshaft and downwardly to lock the camshaft
in the desired position for processing in accordance with
the present invention. Spindle 110 further includes a down-
wardly extending center 120 adapted to be received in the
countersink 30 of the end surface 28 on the camshaft. Drop
pin 122 i8 adapted to be received by bore 32, also on surface
28 so that when pin 122 drops into bore 32, spind$e 110 can
rotate the camshaft through accurately controlled angles
determined by the energizing of drive motor M2.
Lower head 102 is schematically illustrated as having
a rotatable center 110 which will allow rotation of camshaft
C abou~ axis x when the camshaft is driven by motor M2.
Details of lower head 102, as used in practice, are shown in
Figure 10, wherein center 130 is a reciprocal center 130A
having a biasing spring 134. Rotatable spindle 140 is supported
in lower plate 74 by roller bearings, one of which is shown as
roller bearing 144 in Figure 10~ Bellville springs 150 are
mounted on the end of shaft 152 and are held in position by
nut 154. Nut 154 ad~usts the pressure exerted by springs 150
against washer 156 to provide a controlled resistive torque
exerted by upper spindle surface 160 against lower end surface
or bottom surface 40 of camshaft 30. Countersink 42 receives
center 130A. The vertical position of surface 160 is controlled
by the vertical position of spindle 140. Pressure by nut 154
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1~0176 T-7249
determ~nes the amount of force necessary to rotate spindle
1~0 by camshaft C when it is indexed or rotated by motor M2
The reason for this friction is to allow drop pin 122 to
engage bore 32 during initial locating of the camshaft
which concept will be explained later. This location
procedure also involves the structure shown in Figure 2
wherein a movable platen or shuttle 170 is reciprocally
mounted to be moved by cylinder 172 toward lower bearing
18 during the initial locating process. Platen or shuttle
170 carries a proximity switch or detector 180 having an
output line 182. V-notch 190 is a locator arrangement. By
engaging the ~-notch with surface 18, proximity switch or
detector 180 is at a known position with respect to the
surface 22 of cam 20 directly ad;acent lower bearing surface 18.
lS This is better shown in Figure 7A. At this same position, a
mechanical stamp or marker 200 is illustrated. This marker
includes a ram 202 driven toward the portion of the camshaft
to indicate that the camshaft has been processed. V-notch
190 can be formed of a breaking substance to perform the
function of the Bellville springs in Figure 10; however, in
the preferred embodiment, the V-shaped notch is used only for
proximity switch positioning for detection of the lobe during
the initial loading operation.
Figure 2 illustrates the output of proximity switch 180
as it appears in line 182 when shaft C is rotated, The output
in line 182 detects the presence of lobe 26 on the cam
surface adjacent bearing 18. By determining the angular
positions of the first signal caused by the cam lobe and the
last signal caused by the lobe, and then dividing the distance
between these po~itions by two, the location of the specific
lobe is determined. If a proximity switch is used, the
angular position when the switch is turned on by the lobe and
the angular position of the time when the switch is turned
off by removal of the lobe are recorded and divided by two to
produce the actual angular position of the lobe on the parti-
cular cam adjacent bearing 18. Of course, this same reading
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~ ~ ~ O l ~ ~ T-7249
could be taken on any known cam but, in the preferred
embodiment, it is taken upon this lower cam for the purposes
of simplifying the total operation of device D~
Referring now to Figures 5 and 6, induction heating coil
210 is the integral quench type having input leads 212, 214
connected across power supply 220. In practice, this power
supply is a solid state inverter having a frequency of between
10 KHz - 25 KHz and sufficient power to create at least about
20 KW/in of energy at surface 22 of the cams aQ they are being
inductively heated by coil 210. Leads 212, 214 are separated
by insulation material or layer 222 to define a gap G known
as the "fishtail". An annular quench chamber 23a behind
inner cylinder surface 232 of coil 210 directs quenching
fluid outwardly toward axis x through quench`openings 234.
Quenching fluid is introduced into chamber 230 through an
appropriate supply line 236 which is supplied at relatively
high volume to quench surface 22 of cam 20 after it has been
inductively heated by coil 210. Quenching is at a lower
velocity to decrease distinct jet action at the heated surface.
An arcuately shaped flux concentrator formed from a high
permeability material such as Ferrocon is shown as upper and
lower elements 240, 242, respectively. This material is
bonded ferrous particles and is commonly used in induction
heating. These flux concentrater elements circumscribe
substantially less than 180 around surface 232 to cause
increased heating adjacent heel 24 of cam 20 being heated.
The amount of flux concentration material, if any, is
determined by the pattern P to be obtained in cam surface
22, as shown in Figure ~. Immediately below inductor 210
are a pair of reciprocally mounted plates 250~ 252 selectively
movable toward axis x by appropriate operating cylinders 260,
262, respectively. Semi-circular recesses 254, 256 tightly
surround shaft C in the area between a bearing or cams so
that movement of plates 250, 252 toward axis x provide a
small spacing e shown in Figure 6, which is no greater than
; -15-
1 ~ ~ O i7 ~ T-7249
about 0.10 inches. Plates 250, 25~ are as close as possible
below coil 210 so that they cause a lower cavitation effect
from quenching liquid issuing through openings 23~. This
causes a flooding during a quenching operation in a rapid
fashion to rapidly quench out surface 22 after it has been
inductively heated by coil 210. In some instances, plates
250, 252 are just below the surface of coil 210 and have an
axial thickness detenmined by the inner edge of flux con-
centrator 240, as shown in Figure 5. The ob~ect of the plates
is to bring the plates as close as possible to the lower
surface of the induction heating coil so that they assist in
the actual quenching operation. This enhances the efficiency
of the quenching operation, especially in view of the need
for immediate quenching when high power and low cycle times
are employed, as anticipated by the present invention~
Immediately below plates 250, 252 is a cooling assembly
300 having an inner cylindrical surface 302 spacing axis x
and including a plurality of relatively large fluid openings
304 adapted to pass quenching or cooling fluid from inlet
conduit or supply 306 communicated with an annular chamber
308. Plates 250, 252 can rest upon the upper surface of
cooling chamber 300 to reduce the distance c between the
lower edge of induction heating coil 210 and the upper edge
of cooling assembly 300, as shown in Figure 5. This distance
c is reduced to the necessary amount determined by the close
proximity between ad~acent cams 20 as shown in Figure 5.
Distance c is selected 80 that the lower surface 238 of coil
210 i8 below the lower edge 20A of cam 20. The height of
surfsce 232 i8 such that the lower spacing between surface
20a and lower coil surface 238 is substantially as great as
the spacing between the upper face or surface 20b and the
upper face or surface 239 of coil 210. At least, the spacing
c is maintained such that face 232 extends above and below
surface 22 of cam 20 as it is being heated. Further, the
upper surface 310 of cooling assembly 300 is adjacent to or
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.
~30176
T-7249
above the upper face or surface 20b of cam 20 in cooling
assembly 300, as shown in Figure 5. As can be seen,
distance c is relatively small and is as close as possible
to accomplish the geometric objectives discussed above.
The operation of apparatus B as so far described is
now apparent from the showings of Figure 7A - 7H. Upper
head 100 is retracted by actuator 114~ A robot, not shown,
loads camshaft C in the position shown in Figure 1. Counter-
sink 42 of lower surface 40 at bearlng 18 is positioned over
the upwardly extending 130 or 130a. The process i~ then
accomplished as shown in the block diagram of Figure 11.
After the loading procedure, the machine identifies the shaft.
This is done automatically when different shafts are being
provided to the machine; however, in practice a fixed shaft
is to be processed; therefore, no identification is needed.
After the shaft is in position, it is forced downwardly by
actuator 114. This forces lower surface 40 against upper
fixed surface 160 shown in Figure 10. Center 130a is biased
into countersink 42 so that the cam is located between lower
center and upper center 120. Motor M2 is then rotated.
Springs 150 exert a resistance to rotation of spindle 1~0.
- The force between surfaces 40, 160 as shown in Figure 10,
causes a resistance torque to be exerted on cam C. Con-
sequently, upper spindle 110 rotates with respect to upper
surface 28 of camshaft C. This relative movement cont{nues
until pin 122 drops into bore 32. This action locks spindle
110 with camshaft C and overcomes the resistance caused by
springs 150. Thereafter, the camshaft moves with spindle 110
during processing of camsha$t.
Referring again to Figure 11, rotation of the upper head
causes the pin to drop into place. Thereafter, as shown in
Figure 7A, proximity switch 180 carried on platen or shuttle
170 detects the center of the lobe 26 on the particular cam 20
just above bearing 18. This location determines the angular
~ T-7249
disposition of camshaft C with respect to the output of motor
M2 or, other~ise, spindle 110~ This information sets the
program which has already identified the processing steps for
the total processing of cam C in accordance with standard
software concepts using a micro-processor system schematically
disclosed in Figure 9. Marker 200 drives ram 202 against the
camshaft, but not the cam surface, for the purpose of marking
the cam as having been processed. The location of this ram
is selected to mark a position between a cam which cannot be
i}lustrated because the closeness of the structures illustrated
in the drawings.
Thereafter, marker 200 and platen 170 are withdrawn.
This is illustrated in Figure 7B. Motor Ml indexes shaft
C downward until the next ad~acent cam 20 is within heating
co$1 210. This is also shown in Figure 7B. At that time,
plates 250, 252 are moved inwardly as shown in Figure 7C. In
Figure 7D, the heating cycle commences. This is shown by flux
lines at inductor 210. This heating cycle, as explained earlier,
is preferably about 1.0 seconds in length creates a power density
in the neighborhood of 50 KW/in2 and has a frequency of preferably
10 KHz. Before the heating cycle occurs, motor M2 indexes shaft
C circumferentially until lobe 26 is adjacent gap G, as shown
in Figure 6. During this heating cycle, fluid is forced against
lower bearing 18 which has not been hardened. In this manner,
heat in the bearing is minimized. Indeed, it is possible not
to cool at this particular processing step. Referring now
to Figure 7E, the integral quench directs liquid ~a polymer
quench) toward cam 20 from chamber 230. This occurs immediately
and provides a general flooding of the heated sur~ace with
somewhat reduced ~et action. The lower plates 250, 252 prevent
down flushing of liquid to hold liquid within the cylindrical
cavity defined by the inner surface of inductor 210 to rapidly
cool surface 22 of cam 20 through the critical hardness
temperature. As illustrated in this view, the lower cooling
chamber maintains its flow of liquid toward bearing 18.
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T-7249
Turning now to Figure 2F, plates or shields 250, 25~
are retracted. Motor Ml indexes the hardened lower ca~ into
the cooling assembly and brings an unhardened cam into the
induction heating coil 210. Also, motor M2 rotates camshaft
C until the cam is in the proper indexed position as shown in
Figure 6. Thereafter, plates 250, 252 are moved into their
engaging position and the process is repeated as indicated in
the block diagram of Figure 11. First, the hardened cam is
flooded by the cooling assembly. The next cam is then in-
ductively heated and quench hardened. This continuing
operation is illustrated in Figure 7G. At the end of the
cycle, as illustrated in Figure 7H and Figure 8, fuel pump
gear 4~ is moved into coil 210. Motor M2 rotates spindle
210 continuously while gear ~4 is inductively heated and
then quench hardened. Rotation is appropriate here since
gear 44 is circular in shape and requires rotation to prevent
ununiformity adjacent gap G as shown in Figure 8.
As shown in Figure 11, all cam surfaces have now been
hardened on shaft C. The shaft has been shifted downwardly
thrcugh the heating coil to the place where spindle 110 i6
adjacent coil 210 as shown in Figure 7H. The chaft could be
removed and tested in a separate arrangement as shown in
U.S. Patent 4,618,125. In accordance with an aspect
of the present invention, the testing is done
while shafts C, C' are still in device D by an eddy
current arrangement which will be explained later.
Turning again to the reciprocal plates 250, 252 best shown
in Figures 5 and 6, these plates are formed from a relatively
thin tO.20-0.40 inches) electrically insulating, electrically
nonconductive material. Such material is a glass based
laminant with high temperature binder, such as "G10". This
material does not concentrate or direct flux lines created
during the heating portion of the hardening cycle for a cam
surface. Using this material and bringing the plates upwardly
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1~80176 T-7249
close to the bottom o~ coil 210, enhances the quenching
operation by the coil, as well as preventing co~ling liquid
used in cooling assembly 300 from engaging surface 22 during
induction heating. This feature is unique, in combination
with the high frequency, high power and short heating time
for the heating portion of the hardening cycle. All of these
parameters limit the amount of energy into the surface during
the heating cycle, limits the depth of heating and allows
rapid quench hardening to produce a relatively controlled,
shallow hardness pattern P, as shown in Figure 4~ The quenching
liquid ~s a water based polymer which enhances the quenching
operation by removing heat rapidly from surface 22 after it
has been inductively heated. Openings 234 for quenching
are enlarged to allow a low velocity inductor quench impinge-
ment to create a flooding ~uench action on the cam surface,
which is assisted by the lower movable plates 250, 252. Normal
high velocity quenching causes certain variations in the
relatively highly controlled heating pattern. This shows the
advantage of the movable shields. Should the camshaft be
heated in a horizontal position, a shield could be placed on
both sides of inductor 210.
After all camshaft surfaces 22 have been hardened in
accordance with the desired pattern represented in Figure ~,
camshaft C will be in the lower position as shown in Figure 7H.
Thereafter, all surfaces are sequent~ally testet with known
eddy current technology such as illustrated in Mordwinkin
U.S. Patent 4,059,795 and Mordwinkin U.S. Patent 4,230,987.
Other eddy current testing devices are available such as
from Hentschel Instruments, Inc. in Ann Arbor, Michigan.
These devices schematically represented, as eddy current
units 400, 402, apply high frequency through eddy current
testing coils 410, 414. The eddy current reaction caused
by driving these coils is detected through detecting and
powering lines 420. As is well known, the eddy current
~ .
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1 ~ 8~ I7 ~ T-7249
characteristics of the hardened cam surfaces can be deeected
through appropriate lines ~20 to determine metallurgical
characteristics. Referring now to Figure 13, as camshafts
are moved progressively in an upward direction, encoder or
promptors 420 cause units 400, 402 to sense the metallurgi-
cal characteristics at the promptors 430 locate the positions
of the various hardened cams. Consequently, the testing is
progress, i.e., on-the-fly. As the camshaft moves from the
position shown in F~gure 7H in an upward direction, as shown
in Figure 7G, electrical characteristics of coil 410 are read
by line 420 at the time coil 410 is ad~acent a cam 20. This
periodic reading of the output or response of the eddy current
coils is compared to a similar reading made on a plurality of
camshaEts C having physically and manually tested acceptable
surface characteristics. When several acceptable camshafts
are run through the coil 410, a map is constructed statisti-
cally to record the range of acceptable responses from the
eddy current coil 410 as it passes each of the various cams
on a given camshaft. The camshaft remains stationary;
therefore, the maps take in consideration the various cir-
cumferential orientations of the particular values constituting
a given type of camshaft. The map could be a continuous map,
as shown in Figure 12, or a discontinuous map as shown in
Figure 12 A, both of which indicate ranges of acceptable
responses at each cam location. Of course, the promptors 430,
shown in Figure 13, can be program flags and made a part of
the map schematically illustrated in Figures 12 and 12A. This
map, of course, is digitized and need not be visually displayed.
In accordance with the preferred embodiment, a video terminal
450, as shown in Figure 3, is used to display the relationship
of a given cam being scanned by the eddy current coil as it is
compared with acceptable responses generated by a statistical
analysis of acceptable cams tested by hand. As shown in
Figure 12, the dashed line is the output from line 420 of coil
210 during a scanning operation for an acceptable camshaft.
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~ T-7249
As can be seen, the dashed line is read in response to a
promptor ~30 and remains between upper and lower limits.
This is an acceptable cam. The same concept is employed
in the graph shown in Figure 12 wherein promptor ~30 causes
a reading only at the cam areas and these readings are
compared to upper and low limits for these particular cams
being eested in response to a promptor signal or designation
from promptor ~30~
In Figure llA, a block diagram of the A current scanning
function is set forth. The coil traverses the camshaft.
This is accomplished in practice by moving the camshaft with
respect to the coil as so far described. A dual frequency
eddy current device, such as shown in U.S. Patent nu~ 4,230,987,
or any other device drives the coil 410 preferably in a
continuous fashion. The output 420 is then passed to comparator
430 during a prompting time indicated by box 430. These promptors
relate to cams for a particular camshaft. In the comparator
operation 460 of the etdy current system, a selected map for
the given camshaft is used to determine the acceptability of
the responses from lines 420. If the responses are outside of
limits, the particular camshaft is rejected as indicated by
box 470. The map represented by box 480 is loaded selectively
which also determines the promptors 430 for eading the output
420. This particular map is generally fixed in high production
situationsi however, in low production situations, the cam
coming into the device can first be identified either by inditia
or physical characteristics. The id`entified cam has its own
map and cam promptors 430 network. The identification concept
is an option in the block diagra~ of Figure 11. Such identi-
fication will set the program for the processing of the camshaf~
in accordance with Figure 11 and will also load a selected map
480 into the eddy current subroutine of the pr~gram controlling
the operation of the eddy current processing and the camshaft
hardening procedure.
.~
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i~80176 T-7249
Referring n~w to Fig~re 9, the microprocessor employs a
standard I/~ interface 502 with a prom 504 and ram 506~ As
can be seen, the microprocessor controls the various steps
so far explained in ehis device and can include a loadable
program 510 for any particular cam. This load program can
also include identification subroutine together with a
selective loading concept creating a different map shown in
Figure llA and a different program shown in Figure 11~
The current embodiment of the invention in the area of
the induction coil 210 and cooling assembly 300 is shown in
Figures 6A and 6B~ Upper surface 310 is nearly abutting
lower surface 238 of coil 210; therefore, distance c is from
the bottom of a diametrically extending groove 500, one for
each plate 250, 252. These grooves, only one of which is
shown, allow plates 250, 252 to cover the 210 in. diameter
opening 502~ The rest of surface 310 is near surface 238~
Distance c is the about thickness of plates 250, 252, i~e~,
in practice ~125 inches~ Pressure P in chamber 230 is in
the low range of 15-20 p~s~i~ and the openings 234 are in
the general larger ranges of 0~60-0~90 inches~ The polymer
quench liquid is up to about 10~ polymer and, preferably, is
about 4% polymer~ To prevent stray flux from entering the
lower cooling chamber a Ferrocon layer 510 is placed on the
lower surfaces of plates 250, 252 as shown in Figure 6C~
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